Detergent particles

ABSTRACT

Detergent particles obtained by a process comprising the step of dryneutralizing base particles comprising a water-soluble solid alkali inorganic substance (A) with a liquid acid precursor (B) of a non-soap anionic surfactant, wherein the base particles are obtained by a spray-drying method, and wherein the base particles contain the component (A) in an amount of equal to or greater than 4 times the amount equivalent for neutralizing the component (B) and have an average particle size of from 150 to 400 μm; base particles having an average particle size of from 150 to 400 μm, comprising 20 to 80% by weight of a water-soluble solid alkali inorganic substance; a process for preparing detergent particles comprising the steps of (a) preparing a slurry comprising a water-soluble solid alkali inorganic substance (A) in an amount equal to or greater than 4 times the amount equivalent for neutralizing a liquid acid precursor (B) of a non-soap anionic surfactant to be added in step (c); (b) spray-drying the slurry obtained in step (a) to give base particles; and (c) mixing the liquid acid precursor (B) with the base particles obtained in step (b) and dry-neutralizing the resulting mixture; and a detergent composition comprising the detergent particles as defined above. The detergent particles can be used for laundry detergents, dishwashing detergents and the like.

TECHNICAL FIELD

The present invention relates to detergent particles, a process forpreparing the detergent particles, base particles, and a detergentcomposition comprising the detergent particles. More specifically, thepresent invention relates to detergent particles used for washinglaundry items and the like, a process for preparing the detergentparticles, base particles, and a detergent composition comprising thedetergent particles.

BACKGROUND ART

Many detergents comprising an anionic surfactant, such as analkylbenzenesulfonate, as a main component have been prepared from theviewpoints of economic advantage, foaming property and the like. As aprocess for preparing the detergent particles as mentioned above, therehas been employed a process in which an acid precursor of the aboveanionic surfactant is in situ dry-neutralized with a water-soluble solidalkali inorganic substance, such as sodium carbonate, instead ofdirectly adding the surfactant.

For instance, a process of producing a detergent composition comprisingthe steps of dry-neutralizing components in a high speed mixer and/orgranulator at a temperature of 55° C. or less, and thereafter adding aliquid binder thereto to carry out granulation (see Japanese PatentLaid-Open No. Hei 3-33199); a process of producing a detergentcomposition comprising the steps of dry-neutralizing components in ahigh speed mixer and/or granulator at a temperature of 55° C. or more,and then adding a liquid binder thereto to carry out granulation (seeJapanese Patent Laid-Open No. Hei 4-363398); and a process of producinga detergent composition comprising dry-neutralizing components in acontinuous-type high-speed mixer and then increasing the bulk densitywith a moderate-speed mixer, and subsequently cooling and/or drying theproduct to form into granules (see Japanese Patent Laid-Open No. Hei3-146599) have been disclosed.

However, when the detergent particle is produced by these processes, inorder to suppress the particle from being aggregated and/or becomingcoarse due to the adhesive property of the anionic surfactant producedby the neutralization, it is necessary to keep its granular shape byoperating the agitation mechanism for mixing and the cutting mechanismfor disintegration and/or dispersion at high speeds. In this case, thedetergent particle having a desired small particle size can be preparedby optimizing the agitation and/or cutting conditions. However, it wouldbe difficult to efficiently obtain the detergent particle, and theparticle size distribution of the resulting particle would become wider.

As a process for eliminating these problems, a method for preparing adetergent particle having a small particle size at a high yield in whichthe adhesive property of the anionic surfactant can be suppressed bycontaining an inorganic acid in the acid precursor and the content ofthe anionic surfactant can be increased (see WO 98/10052). However,there have yet remain the problems of disintegrating the aggregate byagitation and/or cutting and making the particle size smaller, so thatthere are much room for improvement in the efficiency and the obtainmentof a sharper particle size distribution.

As mentioned above, the process according to dry-neutralization issuitable for conveniently preparing detergent particles comprising ananionic surfactant as a main component. In the conventional process, theprocess is basically carried out by granulating raw materials withdisintegrating, thereby making it difficult to efficiently obtaindetergent particles having a sharp particle size distribution in arelatively small particle size range.

In addition, with regard to the dissolubility, according to theconventional process as described above, the detergent particlescomprise non-hollow particles having a structure in which solidparticles are connected by a large continuous layer of the anionicsurfactant. Therefore, it would not be easy to improve thedissolubility.

Having a sharp particle size distribution in the detergent has anadvantage of not only giving excellent external appearance but alsoimproving its flowability. Also, a detergent comprising an anionicsurfactant as a main component may be used for handwashing in manycases, so that the users' convenience is improved by increasing thedissolubility. Therefore, a sharper particle size distribution and moreimproved dissolubility have been desired in detergent particlescomprising an anionic surfactant as a main component obtained bydry-neutralization.

An object of the present invention is to provide detergent particleshaving excellent storage stability, dissolubility and sharp particlesize distribution, a process for preparing the detergent particles, baseparticles and a detergent composition comprising the detergentparticles.

These and other objects of the present invention will be apparent fromthe following description.

DISCLOSURE OF INVENTION

Accordingly, there are provided:

[1] detergent particles obtained by a process comprising the step ofdry-neutralizing base particles comprising a water-soluble solid alkaliinorganic substance (A) with a liquid acid precursor (B) of a non-soapanionic surfactant, wherein the base particles are obtained by aspray-drying method, and wherein the base particles contain thecomponent (A) in an amount of equal to or greater than 4 times theamount equivalent for neutralizing the component (B) and have an averageparticle size of from 150 to 400 μm;

[2] base particles having an average particle size of from 150 to 400μm, comprising 20 to 80% by weight of a water-soluble solid alkaliinorganic substance;

[3] a process for preparing detergent particles comprising the steps of:

(a): preparing a slurry comprising a water-soluble solid alkaliinorganic substance (A) in an amount equal to or greater than 4 timesthe amount equivalent for neutralizing a liquid acid precursor (B) of anon-soap anionic surfactant to be added in step (c);

(b): spray-drying the slurry obtained in step (a) to give baseparticles; and

(c): mixing the liquid acid precursor (B) with the base particlesobtained in step (b) and dry-neutralizing the resulting mixture; and

[4] a detergent composition comprising the detergent particles asdefined in the above [1].

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an SEM image of a cross section of the base particleobtained in Example 1. In FIG. 1, the cross sections of the externalportion, and the surface portion and the inner portion of the baseparticle are sequentially shown from the left. It can be seen that fineparticles are formed in the inner portion of the base particle in alarge number.

BEST MODE FOR CARRYING OUT THE INVENTION

The detergent particles of the present invention, as described above,are detergent particles obtained by a process comprising the step ofdry-neutralizing base particles comprising a water-soluble solid alkaliinorganic substance (A), with a liquid acid precursor (B) of a non-soapanionic surfactant, wherein the base particles are obtained by aspray-drying method, wherein the base particles contain the component(A) in an amount of equal to or greater than 4 times the amountequivalent for neutralizing the component (B) and have an averageparticle size of from 150 to 400 μm.

In the present invention, since the above detergent particles are used,the water-soluble solid alkali inorganic substance is contained in afine shape in the base particle in an amount far exceeding the amountequivalent for neutralization and the reactive area is increased bymaking the particle size of the base particle itself smaller, so thatthe dry-neutralization is carried out on the surface of the baseparticle with a fast reaction rate. Therefore, the detergent particlescan take a structure in which the base particle is coated with anon-soap anionic surfactant. Therefore, there are exhibited some effectsthat the particle size distribution of the detergent particle has asharp particle distribution on the basis of the base particles obtainedby a spray-drying method and that the yield of the detergent particlesis also dramatically improved. In addition, with regard to thedissolubility, a larger continuous phase is less likely to formed due tothe reaction of the non-soap anionic surfactant with the finewater-soluble solid alkali inorganic substance, and the anionicsurfactant is thinly spread in a filmy state near the surface.Therefore, the dissolution surface area is larger, thereby exhibiting aneffect of an excellent dissolubility.

Furthermore, since the detergent particles have a structure in which thebase particle is coated with the non-soap anionic surfactant, effectsthat stabilities during storage such as bleed-out and caking propertyare dramatically improved are exhibited.

The term “detergent particle” in the present invention refers to aparticle comprising a base particle, a surfactant and the like, and theterm “detergent particles” means an aggregate thereof. Also, thedetergent composition mentioned later means a composition comprising thedetergent particles and separately added deterging components other thanthe detergent particles, such as fluorescers, enzymes, perfumes,defoaming agents, bleaching agents and bleaching activators.

Composition for Base Particles

The “base particle” constituting the detergent particle contained in thedetergent particles of the present invention comprises the component(A), which is used for dry-neutralizing with the component (B), and thebase particle is a particle obtained by a spray-drying method. Anaggregate thereof is referred to as “base particles.”

1. Component (A): Water-Soluble Solid Alkali Inorganic Substance

The term “water-soluble solid alkali inorganic substance” of thecomponent (A) refers to an alkali inorganic substance which is solid atan ambient temperature, and one which can be dissolved in water in anamount of 1 g or more in 100 g of water at 20° C. is preferable. Thewater-soluble solid alkali inorganic substance is not particularlylimited, and alkali metal salts, silicates and the like having hydroxylgroup, carbonate group, or hydrogencarbonate group can be used. Thewater-soluble solid alkali inorganic substance includes, for instance,sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassiumcarbonate, sodium silicate and the like. Among them, sodium carbonate ispreferable as an alkalizing agent showing suitable pH buffering range ina washing liquid. Also, the formulation of sodium hydroxide is alsoeffective from the viewpoint of the reaction rate during thedry-neutralization.

In the present invention, it is preferable that the component (A) existsin as fine state as possible in the base particles. For instance, thesize of the component (A) is such that its average particle size ispreferably from 0.1 to 50 μm. The state of this particle can beconfirmed by direct observation with the SEM.

In the present invention, when the detergent particles are prepared byusing the base particles comprising fine particles of the component (A),the dry-neutralization can be carried out without applying high cuttingpower as conventionally required when the above base particles are mixedwith a liquid acid precursor (B) of a non-soap anionic surfactant, sothat the base particle undergoes little disintegration, whereby theresulting detergent particle has little change in the particle growth ofthe base particle. Therefore, the particle size distributions of thebase particles and the detergent particles become sharp. Accordingly,there is an advantage that a detergent particle having low bulk density,excellent storage stability and dissolubility and sharp particle sizedistribution can be efficiently obtained.

As to the amount of the component (A), in addition to the amountnecessary from the viewpoint of detergency performance, an amountnecessary for dry-neutralization of the component (A) with the liquidacid precursor (B) of a non-soap anionic surfactant to be mixed in step(c) must be formulated. Further, it is necessary that the reaction ofthe component (A) with the component (B) is accelerated on the surfaceof the detergent particle. Therefore, it is necessary that the amount ofthe component (A) is 4 times or more, preferably 6 times or more, of theamount equivalent for neutralizing the component (B). Concretely, theamount of the component (A) is preferably from 20 to 80% by weight, morepreferably from 25 to 70% by weight, still more preferably from 30 to60% by weight, of the base particles, from the viewpoints of reactionrate and degree of freedom in the formulation.

In addition, the amount of the component (A) is preferably 10% by weightor more, more preferably 15% by weight or more, of the detergentparticles from the viewpoint of detergency performance. On the otherhand, the amount of the component (A) is at least the amount equivalentfor neutralizing the liquid acid precursor (B) from the viewpoint ofdry-neutralization. Therefore, the formulation amount is preferablyequal to or greater than the sum of these two values.

An essential component for the base particles in the present inventionis only the water-soluble solid alkali inorganic substance (A), andother components usually used in the detergent particles can beoptionally simultaneously formulated in the base particles in properamounts, from the viewpoints of the detergency performance, the particlesize distribution and the particle strength. The other componentsinclude a chelating agent, a water-soluble inorganic salt, a(water-soluble) polymer, a surfactant, a water-insoluble excipient,other auxiliary components and the like. Among them, it is preferablethat the chelating agent, the water-soluble inorganic salt, the(water-soluble) polymer and the surfactant are formulated. Concreteexamples of these components are given hereinbelow.

2. Chelating Agent

The chelating agent can be formulated in the base particles in order tosuppress the inhibition of deterging action by metal ions, and examplesthereof are water-soluble chelating agents and water-insoluble chelatingagents.

As the amount of the chelating agent, it is desired that the amount ofthe chelating agent formulated in the base particle is adjusted so thatthe content of the chelating agent is preferably from 3 to 60% byweight, more preferably from 5 to 40% by weight, still more preferablyfrom 10 to 40% by weight, of the detergent particles, from the viewpointof metal ion capturing ability. A plural chelating agents can besimultaneously formulated, in which case it is desired that its totalcontent is as specified above.

The water-soluble chelating agent is not particularly limited as long asthe water-soluble chelating agent is a substance having a metal ioncapturing ability, and tripolyphosphate, orthophosphate, pyrophosphateand the like can be used. Among them, tripolyphosphate is preferable,and its content is preferably 60% by weight or more, more preferably 70%by weight or more, still more preferably 80% by weight or more, of theentire water-soluble chelating agents. Also, as the counter ion, analkali metal ion is preferable, and especially sodium ion and/orpotassium ion is preferable.

The water-insoluble chelating agent may be added to the base particlesfor the purposes of improving the metal ion capturing ability andenhancing the strength of the base particle. Those having an averageparticle size of from 0.1 to 20 μm are preferable from the viewpoint ofthe dispersibility in water. Preferable base materials includecrystalline aluminosilicates, including, for instance, A-type zeolite,P-type zeolite, X-type zeolite and the like. The A-type zeolite ispreferable from the viewpoints of the metal ion capturing ability andeconomic advantages.

As to the amount of the zeolite formulated, when the zeolite isformulated in a large amount, there is a possibility that the zeolitedecomposes during the dry-neutralization reaction. Therefore, it ispreferable that the amount of the zeolite is controlled to 10% by weightor less of the base particles. Also, for the purpose of suppressing thedecomposition, the amount of zeolite formulated can be increased byusing the zeolite together with a water-soluble alkalizing agent havinghigh dissolubility and high alkali strength, such as sodium hydroxide.

3. Water-Soluble Inorganic Salt

It is preferable that the water-soluble inorganic salt is formulated inthe base particles in order to enhance the ionic strength of the washingliquid and improve the effects of sebum stain deterging and the like.The water-soluble inorganic salt is not particularly limited as long asthe water-soluble inorganic salt is a substance having an excellentdissolubility and not giving worsening effect to detergency. Thewater-soluble inorganic salt includes, for instance, an alkali metalsalt or ammonium salt having sulfate group or sulfite group, and thelike. Among them, it is preferable that sodium sulfate, sodium chloride,sodium sulfite or potassium sulfate having high degree of ionicdissociation is used as an excipient. Also, its combined use withmagnesium sulfate is also effective from the viewpoint of improving thedissolution speed.

The amount of the water-soluble inorganic salt is preferably from 5 to80% by weight, more preferably from 10 to 70% by weight, still morepreferably from 20 to 60% by weight, of the base particles, from theviewpoint of the ionic strength.

4. (Water-Soluble) Polymer

The water-soluble polymer may be added to the base particles for thepurposes of enhancing the particle strength by adjustment ofprecipitation of crystals and film formation on the base particles. Thewater-soluble polymer includes organic polymers and inorganic polymers.For instance, the organic polymer includes carboxylate polymers,carboxymethyl cellulose, soluble starches, saccharides, polyethyleneglycol and the like, and the inorganic polymer includes amorphoussilicates and the like. Among them, the carboxylate polymers arepreferable, among which a salt of an acrylic acid-maleic acid copolymerand a polyacrylate (counter ions: Na, K, NH₄ and the like) areespecially preferable. Those carboxylate polymers having a molecularweight of from 1000 to 8000 are preferable, and those having a molecularweight of 2000 or more and 10 or more carboxylate groups are morepreferable. The amount of the organic polymer is preferably from 0.1 to10% by weight, more preferably from 0.5 to 5% by weight, of the baseparticles.

In addition, it is preferable that the organic polymer is used togetherwith the inorganic polymer such as amorphous silicates, from theviewpoint of enhancing the particle strength, especially No. 2 sodiumsilicate is preferable. The amount of the inorganic polymer ispreferably 15% by weight or less, more preferably 10% by weight or less,still more preferably 5% by weight or less, of the base particles, fromthe viewpoint of the dissolubility.

5. Surfactant

The surfactant may be added for the purpose of controlling the bulkdensity. For instance, a linear sodium alkylbenzenesulfonate, a sodiumalkylsulfonate, sodium ether sulfonate, sodium paratoluenesulfonate,sodium xylenesulfonate, sodium cumenesulfonate, or the like can be used.Especially, the linear sodium alkylbenzenesulfonate is preferable fromthe viewpoint of economic advantages.

The amount of the surfactant is preferably 0.05% by weight or more, morepreferably 0.1% by weight or more, of the base particles, from theviewpoint of controlling the bulk density. On the other hand, the amountof the surfactant is preferably 10% by weight or less, more preferably5% by weight or less from the viewpoint of the dissolubility.

In addition, these surfactants can be added in the form of liquid acids,not neutralized form. In this case, it is preferable that the alkalizingagent is added in an amount equal to or greater than the amountequivalent for neutralizing the liquid acid, and the addition of sodiumhydroxide is especially preferable.

6. Water-Insoluble Excipient

The water-insoluble excipient is not particularly limited as long as thewater-insoluble excipient has excellent dispersibility in water and doesnot give worsening effects to detergency. The water-insoluble excipientincludes, for instance, crystalline or amorphous aluminosilicates,silicon dioxide, hydrated silicic acid compound, clay compounds such asperlite and bentonite, and the like. It is preferable that thewater-insoluble excipient has an average primary particle size of from0.1 to 20 μm, from the viewpoint of the dispersibility in water.

The amount of the water-insoluble excipient is preferably 50% by weightor less, more preferably 30% by weight or less, of the base particles,from the viewpoints of economic advantages and the dispersibility.

7. Other Auxiliary Components

A fluorescer, a pigment, a dye or the like may be formulated in the baseparticles.

8. Preferable Combination

Among the compositions mentioned above, it is preferable that sodiumcarbonate/sodium sulfate/sodium polyacrylate are used in combination,and it is more preferable that sodium carbonate/sodium sulfate/sodiumpolyacrylate/sodium tripolyphosphate are used in combination, from theviewpoint of precipitating a larger amount of fine crystals, therebyenhancing the particle strength.

In addition, when base particles having a lower bulk density areprepared, it is preferable to add a surfactant in addition to theabove-mentioned combination.

The base particles used in the present invention can be obtained byspray-drying a slurry prepared by adding the above components withmixing. The water content of the slurry and the spray-drying conditionsare not particularly limited.

Detergent Particles

The “detergent particle” contained in the detergent particles of thepresent invention refers to a particle obtained by dry-neutralizing abase particle containing a water-soluble solid alkali inorganicsubstance (A) with a liquid acid precursor (B) of a non-soap anionicsurfactant, and an aggregate thereof is referred to as “detergentparticles.”

1. Base Particles

The amount of the base particles in the detergent particles is notparticularly limited. The amount of the base particles is preferably 40%by weight or more, more preferably 50% by weight or more, still morepreferably 60% by weight or more, of the detergent particles, from theviewpoints of maintaining the particle size distribution and improvingthe dissolubility. On the other hand, the amount of the base particlesis preferably 85% by weight or less, more preferably 75% by weight orless, of the detergent particles, from the viewpoint of the degree offreedom in the formulation.

2. Component (B): Liquid Acid Precursor of Non-Soap Anionic Surfactant

The component (B) of the detergent particles is formulated as the liquidacid precursor of a non-soap anionic surfactant, of which a part or allof the component (B) react with the component (A) in the base particles.

The liquid acid precursor of a non-soap anionic surfactant, which is thecomponent (B), refers to a precursor of a non-soap anionic surfactant,which has an acidic form and is liquid, and is capable of forming a saltby the neutralization reaction. Therefore, the liquid acid precursor ofthe non-soap anionic surfactant is not particularly limited as long asit is a precursor of a known anionic surfactant having theabove-mentioned characteristics. The liquid acid precursor of a non-soapanionic surfactant includes a linear alkylbenzenesulfonic acid (LAS),α-olefinsulfonic acid (AOS), an alkylsulfuric acid (AS), an internalolefinsulfonic acid, fatty acid esters of sulfonic acid, an alkyl ethersulfuric acid, a dialkyl sulfosuccinic acid and the like. The component(B) as mentioned above may be used as a single component or in admixtureof two or more components. Among them, the linear alkylbenzenesulfonicacid (LAS) is preferable from the viewpoints of economic advantages,storage stability and foaming property.

The amount of the component (B) is preferably 10 parts by weight ormore, more preferably 15 parts by weight or more, still more preferably20 parts by weight or more, especially preferably 25 parts by weight ormore, based on 100 parts by weight of the base particles, from theviewpoints of the detergency and the storage stability. On the otherhand, the amount of the component (B) is preferably 80 parts by weightor less, more preferably 60 parts by weight or less, still morepreferably 40 parts by weight or less, based on 100 parts by weight ofthe base particles, from the viewpoints of maintaining sharpness of theparticle size distribution and suppressing the loss of dissolubility bythe continuous phase of the neutralized product of the component (B).

In the present invention, it is preferable that the surface of the baseparticle is substantially coated with the non-soap anionic surfactant,from the viewpoint of the storage stability. The specific surface areaincreases when the bulk density is lowered, so that the preferableamount of the neutralized product of the component (B) also increases.If the surface of the base particle is not coated with the neutralizedproduct of the component (B), there is a risk of generating blockingcaused by the water-soluble inorganic salt on its surface.

3. Component (C): Fluidizing Aid

In the detergent particles of the present invention, the particle issubjected to surface modification with a fluidizing aid for the purposeof further improving the flowability and the storage stability of thedetergent particle.

As the fluidizing aid, those known ones usually employable can be used,and sodium tripolyphosphate, a crystalline or amorphous aluminosilicate,diatomaceous earth, silica and the like can be preferably used. Amongthem, sodium tripolyphosphate and zeolite, each having a chelatingability, are preferable. By surface modifying the particle with asubstance having a chelating agent, the chelating agent acts from theinitial stage of washing, whereby improving the deterging performance.The zeolite is more preferable from the viewpoint of the flowabilityproperties, and sodium tripolyphosphate is more preferable from theviewpoint of rinsing ability.

It is desired that the particle to be used as the fluidizing aid has anaverage particle size of one-tenth or less that of the average particlesize of the detergent particles, from the viewpoint of coating ability.

In addition, when the amount of the fluidizing aid is too much or toolittle, the flowability properties are lowered. Therefore, the amount ofthe fluidizing aid is preferably from 2 to 20% by weight, morepreferably from 5 to 15% by weight of the detergent particles.

When the zeolite is used as the fluidizing aid, it is preferable thatthe surface modification is carried out after the termination of theneutralization reaction from the viewpoint of suppression of thedecomposition.

4. Other Components

The detergent particles of the present invention can be optionallyformulated in proper amounts of the substances listed below.

(1) Inorganic Acid

When the base particles are mixed with the liquid acid precursor (B) ofa non-soap anionic surfactant, an inorganic acid can be added for thepurpose of reducing the adhesive property by the produced non-soapanionic surfactant. Preferable inorganic acids usable in the presentinvention include sulfuric acid and phosphoric acid, and a morepreferable inorganic acid includes sulfuric acid.

The amount of the inorganic acid formulated is preferably from 0.3 to1.0 mol, more preferably from 0.3 to 0.8 mol, still more preferably from0.35 to 0.7 mol, per one mol of the component (B).

(2) Aqueous Alkali Solution

For the purpose of accelerating the dry-neutralization reaction, anaqueous alkali solution can be added to the base particles as a reactioninitiator. The amount of the aqueous alkali solution added is preferablyfrom 0.05 to 0.5 times the amount equivalent for neutralizing the liquidacid precursor (B) of the non-soap anionic surfactant, more preferablyfrom 0.10 to 0.45 times the amount equivalent for neutralizing theliquid acid precursor, especially preferably from 0.15 to 0.40 times theamount equivalent for neutralizing the liquid acid precursor. The amountof the aqueous alkali solution is preferably 0.05 times or more of theamount equivalent for neutralizing the liquid acid precursor, from theviewpoint of initiating the neutralization reaction to give desiredeffects, and is preferably 0.5 times or less of the amount equivalentfor neutralizing the liquid acid precursor, from the viewpoint ofsuppressing the aggregation of the detergent particle. The concentrationof the aqueous alkali solution is not particularly limited. In order tosuppress the dissolution of the base particles, the concentration of theaqueous alkali solution is preferably from 20 to 50% by weight, morepreferably from 30 to 50% by weight, still more preferably from 40 to50% by weight.

The kind of the aqueous alkali solution is not particularly limited. Theaqueous alkali solution includes, for instance, aqueous strong-alkalisolutions which easily cause neutralization reactions with the liquidacid precursor (B) of a non-soap anionic surfactant, such as an aqueoussodium hydroxide solution and an aqueous potassium hydroxide solution.Among them, the aqueous sodium hydroxide solution is preferred from theviewpoint of economic advantages. In addition, it is more preferablethat the aqueous alkali solution has a pH of 12 or more.

(3) Water-Soluble Solid Alkali Inorganic Substance (A) For the purposeof accelerating the dry-neutralization reaction, the above-mentionedwater-soluble solid alkali inorganic substance (A) can be added in asolid state as a reaction initiator. It is preferable that the component(A) is added as powder which is as fine as possible from the viewpointof the reactivity, and it is more preferable that the component (A) isused together with the aqueous alkali solution.

The amount of the component (A) is preferably equal to or smaller thanthe amount equivalent for neutralizing the non-soap anionic surfactant,from the viewpoints of suppressing the inhibition of the reaction withthe base particles and maintaining the particle size distribution.

(4) Surfactant

A surfactant which is liquid at an ambient temperature may be added,from the viewpoint of improving the detergency, within the range so asnot to affect the storage stability and the flowability properties andnot to increase the bulk density to be equal to or greater than thedesired level. The surfactant includes, for instance, nonionicsurfactants, such as polyoxyalkylene alkyl(8 to 20 carbon atoms) ethers,alkyl polyglycosides, polyoxyalkylene alkyl(8 to 20 carbon atoms) phenylethers, polyoxyalkylene sorbitan fatty acid(8 to 22 carbon atoms)esters, polyoxyalkylene glycol fatty acid(8 to 22 carbon atoms) esters,polyoxyethylene polyoxypropylene block polymers, and the like.

In addition, the surfactant which is liquid at an ambient temperaturehas an effect of lowering the viscosity of the non-soap anionicsurfactant, thereby accelerating the penetration of the surfactant intothe base particle. When the surfactant is added, the detergent particlehas a controlled particle growth and improved granulation yield.

The amount of the surfactant which is liquid at an ambient temperatureis preferably 10% by weight or less, more preferably 5% by weight orless, still more preferably 3% by weight or less, of the detergentparticles, from the viewpoint of suppression of bleed-out and thefoaming property. On the other hand, the amount of the surfactant ispreferably 1% by weight or more, more preferably 2% by weight or more,from the viewpoint of acceleration of the penetration.

(5) Water

Water may be added to the detergent particle for the purpose of loweringthe viscosity of the non-soap anionic surfactant, thereby acceleratingthe penetration of the surfactant into the base particle. The amount ofwater is preferably 1% by weight or more, more preferably 2% by weightor more, of the detergent particles, from the viewpoint of accelerationof the penetration. The amount of water is preferably 5% by weight orless, more preferably 3% by weight or less, of the detergent particles,from the viewpoint of suppression of excess granulation.

Also, this water may be used as water for dissolving the above inorganicsalt and the surfactant.

The amount of the surfactant which is liquid at an ambient temperatureis preferably 10% by weight or less, more preferably 5% by weight orless, still more preferably 3% by weight or less, of the detergentparticles, from the viewpoints of suppression of bleed-out and foamingproperty.

Detergent Composition

The detergent composition of the present invention comprises separatelyadded detergent components other than the detergent particles (forinstance, fluorescers, enzymes, perfumes, defoaming agents, bleachingagents, bleaching activators, and the like). In this case, it ispreferable that the detergent composition comprises the detergentparticles according to the present invention in an amount of preferably50% by weight or more, more preferably 60% by weight or more, still morepreferably 80% by weight or more. Since the detergent composition hasthe above constitution, a detergent composition having excellent storagestability, dissolubility and sharp particle size distribution can beprovided.

Preparation Process of Detergent Particles

The process for preparing detergent particles of the present inventionis characterized in that the process comprises the steps of:

(a): preparing a slurry comprising a water-soluble solid alkaliinorganic substance (A) in an amount equal to or greater than 4 timesthe amount equivalent for neutralizing a liquid acid precursor (B) of anon-soap anionic surfactant to be added in step (c); and

(b): spray-drying the slurry obtained in step (a) to give baseparticles;

(c): mixing the liquid acid precursor (B) with the base particlesobtained in step (b), and dry-neutralizing the resulting mixture.

Since the process for preparing detergent particles of the presentinvention comprises the above steps (a) to (c), there is an advantagethat detergent particles having a sharp particle size distribution in arelatively small particle size range can be efficiently obtained.

The steps (a) to (c) will be described in detail hereinbelow.

1. Step (a)

In the step (a), it is important that the water-soluble solid alkaliinorganic substance (A) is formulated so that the inorganic substance isfinally made finer in the base particles, from the viewpoints ofincreasing the reaction rate and enhancing the particle strength. Theprocess for making the water-soluble solid alkali inorganic substance(A) finer includes the following processes.

(1) Formulation as Dissolved Component

The water-soluble solid alkali inorganic substance (A) exists in theslurry in a dissolved state. In this case, the inorganic substance isformed into fine particles as the component (A) alone or a complex saltwith other components during spray-drying.

(2) Precipitation of Crystals in Slurry

The dissolved water-soluble solid alkali inorganic substance (A) isprecipitated by controlling the solubility of the component (A). Theprecipitated crystal may solely consists of the component (A) or form acomplex salt with another component. In this case, it is preferable thatthe solubility is controlled by adding other water-soluble components inorder to produce fine crystals. In addition, the addition of the polymeris also effective as a crystal-controlling agent in order to suppressthe crystal from growing larger.

(3) Pulverization in Slurry

The crystals can be made finer by pulverizing coarse grains derived fromraw materials, crystals of a complex salt reacted in coarse grain stateand crystals of largely grown complex salt by the precipitation, with awet-type pulverizer, such as line mills, colloidal mills and mediamills.

By combining these processes (1) to (3), the water-soluble solid alkaliinorganic substance can be formulated in the base particles in the formof fine particles. In order to sufficiently exhibit the reactivity inthe base particles, the size of the fine particles in the above (2) and(3) is such that their average particle size in the slurry is preferably50 μm or less, more preferably 30 μm or less, still more preferably 20μm or less.

The conditions for the preparation of the slurry are not particularlylimited as long as the base particles satisfy the above-describedcomposition. In order to improve the particle strength of the baseparticles, it is desired to employ a preparation process which allowsthe precipitation of fine crystals in the slurry in a large amount. Thefine crystal as referred to herein includes not only the crystalcontaining the water-soluble solid alkali inorganic substance (A) butalso the crystal not containing an alkali, such as the crystal of sodiumtripolyphosphate or the crystal of sodium sulfate.

The water content of the slurry is preferably 60% by weight or less,more preferably 55% by weight or less, from the viewpoint of theprecipitation of the crystals. On the other hand, the water content ofthe slurry is preferably 40% by weight or more, more preferably 45% byweight or more, from the viewpoint of easy handling.

The preparation temperature of the slurry is preferably 30° C. orhigher, more preferably 40° C. or higher, from the viewpoint of thesolubility. On the other hand, the preparation temperature of the slurryis preferably 80° C. or lower, more preferably 70° C. or lower, from theviewpoint of the thermal stability.

In addition, the order of the addition of each of the components duringthe preparation of the slurry greatly affects the precipitation of thecrystals. The order of the formulation for the preferable compositionmentioned above is, for instance, the order of the formulation mentionedbelow.sodium tripolyphosphate→sodium sulfate→sodium polyacrylate→sodiumcarbonatesodium sulfate→sodium tripolyphosphate→sodium polyacrylate→sodiumcarbonatesodium tripolyphosphate→sodium carbonate→sodium polyacrylate→sodiumsulfate

Besides the above, the fine crystals can be precipitated in a largeamount by a process such as a process comprising making the temperaturedifference (ΔT) between the slurry and the jacket larger, or a processcomprising applying a shearing force to the slurry with a line mill orthe like during the preparation and/or after the preparation of theslurry.

Besides the method of precipitating fine crystals in a large amount,other components can be added from the viewpoints of the particlestrength and the stabilization of the slurry. For instance, it ispreferable that sodium silicate is firstly added from the viewpoint ofenhancing the particle strength, and that sodium chloride is finallyadded from the viewpoint of stabilization of the slurry.

2. Step (b)

The step (b) comprises spray-drying the slurry obtained in step (a) togive base particles. The conditions for spray-drying the slurry obtainedin the step (a) are not particularly limited, as long as the substancesformulated in the slurry are not substantially affected, andspray-drying conditions generally carried out can be employable.

The spray-drying temperature is preferably from 150° to 300° C., morepreferably from 170° to 250° C., from the viewpoints of improving thedrying efficiency and suppressing the decomposition. On the other hand,as the device for carrying out spray-drying, a usually knownspray-drying tower can be used. It is preferable that the exhaust airtemperature of the spray-drying tower is adjusted to 80° to 130° C.

During the spray-drying in the present invention, it is important toobtain the base particle having a relatively small particle size with asharp particle size distribution. For this purpose, it is important toselect the nozzle type and its spraying pressure. For instance, theabove-mentioned object can be achieved by using a single-fluid-typehigh-pressure nozzle.

3. Step (c)

The step (c) comprises mixing the liquid acid precursor (B) of anon-soap anionic surfactant with the base particles obtained in step(b), to carry out dry-neutralization. It is preferable that thecomponent (B) is mixed as homogeneously as possible with the baseparticles.

As the process for adding the component (B), it is preferable that thecomponent (B) is added as homogeneously as possible by spraying thecomponent (B) with a nozzle. The temperature at which the component (B)is added is preferably from 40° to 80° C., more preferably from 50° to70° C., from the viewpoint of the flowability.

The dry-neutralization temperature is preferably the higher the better,from the viewpoint of accelerating the reaction, and thedry-neutralization temperature is preferably from 60° to 80° C. On theother hand, the dry-neutralization temperature is the lower the better,from the viewpoints of delaying the reaction, and extending the mixedstate with the liquid acid, thereby uniformly coating the surface of theparticle, and the dry-neutralization temperature is preferably from 20°to 40° C.

Also, during the dry-neutralization, the aggregation of the detergentparticles is likely to be generated because the component (B) becomesmore viscous by the neutralization. A process for suppressing theaggregation includes a process comprising allowing air draft during theneutralization reaction, thereby lowering the adhesive property of thesurface of the surfactant. Also, it is also effective to add aninorganic acid to the component (B), thereby forming an inorganic saltat the same time as the formation of the surfactant.

On the other hand, in order to accelerate the dry neutralization, theaqueous alkali solution or the water-soluble solid alkali inorganicsubstance (A) can be added to the base particles before the addition ofthe liquid acid.

In the step (c), it is preferable that the cutting power during theneutralization is reduced as much as possible in order to suppress thedisintegration of the base particles during the dry neutralization. Itis more preferable that only a mixing mechanism is used, and a cuttingpower by a cutting mechanism such as a chopper is not applied. The mixerin which the above-described cutting power is not applied includes, forinstance, a Ribbon Mixer, a Nauta Mixer and the like. Even in a casewhere a device equipped with a cutting mechanism, such as a Lödige Mixeror a High-Speed Mixer, is used, the disintegration of the base particlescan be suppressed by reducing a cutting power with a low-speed rotationof the chopper or without using the cutting mechanism. In addition, evenif the cutting power were not applied, since the base particle comprisesa water-soluble solid alkali inorganic substance in the form as fine aspossible in an amount far exceeding the amount equivalent forneutralization, dry-neutralization can be easily carried out on thesurface of the base particle.

4. Step (d)

It is preferable that the step comprising surface-modifying is carriedout with a fluidizing aid [step (d)] in order to further improve theflowability properties and the storage stability of the detergentparticle obtained in the step (c) of which surface is coated with thenon-soap anionic surfactant.

The conditions for the surface modification are not particularlylimited, and it is preferable that the fluidizing aid is distributed onthe surface of the detergent particle as uniformly as possible.

The temperature in the device for surface modification is notparticularly limited. It is preferable that the surface modification iscarried out with cooling from the viewpoint of solidifying thesurfactant.

The device for surface modification is preferably a device which cangive a strong agitating power and cutting power at the same time, andmodify the surface uniformly. As the device described above, a LödigeMixer and a High-Speed Mixer are suitably used.

The properties of the base particles and the detergent particles of thepresent invention, and the methods for determining the propertiesthereof will be described hereinbelow.

Properties of Base Particles

One of the features of the present invention resides in that a baseparticle capable of rapidly reacting with a liquid acid precursor of anon-soap anionic surfactant, to fix the surfactant on its surface isprovided. For this purpose, a large amount of the alkali is formulated,made finer and spray-dried. It is preferable that the particle afterspray-drying satisfies the following properties.

The base particles have an average particle size of from 150 to 400 μm,preferably from 200 to 300 μm, from the viewpoints of the reactivity andthe flowability.

The base particles have a particle strength of preferably 100 kg/cm² ormore, more preferably 200 kg/cm² or more, from the viewpoint ofsuppression of the disintegration during the dry-neutralization.

The base particles have a water content of preferably 10% by weight orless, more preferably 5% by weight or less, still more preferably 3% byweight or less, from the viewpoints of easy handling and the storagestability.

In addition, the bulk density of the base particles is preferably thesame as, or slightly lower than, that of the detergent particles, and itis desired that the bulk density is lower than the desired bulk densityby 50 to 100 g/L or so. Here, when the surfactant which is liquid at anambient temperature or water is used together, it is preferable that thebulk density is lower than the desired bulk density by 100 to 200 g/L orso.

Properties of Detergent Particles

It is preferable that the detergent particles in the present inventionare prepared by dry-neutralization, while the particle size distributionand the shape of the base particles are maintained as much as possible.Therefore, the properties of the detergent particles are greatlyaffected by the properties of the base particles, and the desireddetergent particles can be obtained by using the above-mentioned baseparticles.

Specifically, the detergent particles have an average particle size ofpreferably from 150 to 500 μm, more preferably from 180 to 300 μm, fromthe viewpoints of easy handling and the external appearance.

The detergent particles have a water content of preferably 10% by weightor less, more preferably 5% by weight or less, still more preferably 3%by weight or less, from the viewpoint of the storage stability.

Also, the detergent particles have a bulk density of preferably from 150to 800 g/L, more preferably from 250 to 600 g/L, still more preferablyfrom 300 to 500 g/L.

Among the detergent particles having these properties, detergentparticles comprising a detergent particle in which the size of theabove-mentioned base particle is retained are preferable. Here, theretention of the shape of the base particle is evaluated by the degreeof particle growth of the detergent particle. The degree of particlegrowth is preferably from 0.9 to 1.6, more preferably from 0.9 to 1.4.The degree of particle growth can be determined by the followingequation: $\text{Degree~~of~~Particle~~Growth} = \frac{\begin{matrix}\text{Average~~Particle~~Size~~of} \\\text{Final~~Detergent~~Particles}\end{matrix}}{\begin{matrix}\text{Average~~Particle~~Size~~of} \\\text{Base~~Particles}\end{matrix}}$The “final detergent particles” refer to particles obtained after dryneutralization or, when subjected to a surface modification step,particles obtained by the surface modification step.

Methods for Evaluation of Properties

The methods for determining the properties of the above-mentioned baseparticles or detergent particles are described below.

1. Bulk Density

The bulk density is measured by a method according to JIS K 3362.

2. Average Particle Size

The average particle size is measured by vibrating a sample for 5minutes using standard sieves (sieve-openings: 2000 to 125 μm,)according to JIS Z 8801, and thereafter calculating the median size froma weight percentage according to the size openings of the sieves.

3. Particle Strength

The method for measuring the particle strength is as follows.

A cylindrical vessel of an inner diameter of 3 cm and a height of 8 cmis charged with 20 g of a sample, and the sample-containing vessel(manufactured by TSUTSUI RIKAGAKU KIKAI CO., LTD., “Model TVP1”tapping-type close-packed bulk density measurement device; tappingconditions: period 36 times/minute, free fall from a height of 60 mm) istapped for 30 times. The sample height (an initial sample height) atthat time is measured. Thereafter, an entire upper surface of the samplekept in the vessel is pressed at a rate of 10 mm/min with a pressingmachine to take measurements for a load-displacement curve. The slope ofthe linear portion at a displacement rate of 5% or less is multiplied byan initial sample height, and the resulting product is divided by apressed area, to give a quotient which is defined as the particlestrength.

4. Average Particle Size of Fine Particles

As to the fine particles in the slurry, the average particle size can bedetermined, using, for instance, an FBRM system (manufactured by METTLERTOLEDO) without diluting the slurry.

When the FBRM system is used, 1 L of a slurry to be determined issupplied in a 1-L plastic cup, and a probe is inserted therein at anangle of 40 to 45° to the liquid surface and placed so that adetermining surface of the probe does not appear above the liquidsurface. Next, the slurry is agitated at 250 r.p.m. (r/min) using apropeller having a diameter of 6 cm, and the determination is made afterconfirming the determining surface of the probe is in the slurry.Incidentally, the plastic cup is kept in a water bath so as to have thesame temperature as that the preparation temperature for the slurry.

5. Dissolubility

As the index for the dissolubility of the detergent particles in thepresent invention, there can be employed the 60-seconds dissolutionratio of the detergent particles. The dissolution ratio is preferably90% or more, more preferably 95% or more. Incidentally, thedissolubility of the detergent composition can also be evaluated in thesame manner.

The 60-seconds dissolution ratio of the detergent particles iscalculated by the method described below.

A 1-L beaker (a cylindrical form having an inner diameter of 105 mm anda height of 150 mm, for instance, a 1-L glass beaker manufactured byIwaki Glass Co., Ltd.) is charged with 1 L of hard water cooled to 5° C.and having a water hardness corresponding to 71.2 mg CaCO₃/L (a molarratio of Ca/Mg: 7/3). With keeping the water temperature constant at 5°C. with a water bath, water is stirred with a stirring bar [length: 35mm and diameter: 8 mm, for instance, Model “TEFLON SA”(MARUGATA-HOSOGATA), manufactured by ADVANTEC] at a rotational speed(800 r.p.m.), such that a depth of swirling to the water depth is about⅓. The detergent particles which are accurately sample-reduced andweighed so as to be 1.0000 g±0.0010 g are supplied and dispersed inwater with stirring, and stirring is continued. After 60 seconds fromsupplying the particles, a liquid dispersion of the detergent particlesin the beaker is filtered with a standard sieve (diameter: 100 mm)having a sieve-opening of 74 μm as defined by JIS Z 8801 of a knownweight. Thereafter, water-containing detergent particles remaining onthe sieve are collected in an open vessel of a known weight togetherwith the sieve. Incidentally, the operation time from the start offiltration to collection of the sieve is set at 10 sec±2 sec. Theinsoluble remnants of the collected detergent particles are dried forone hour in an electric dryer heated to 105° C. Thereafter, the driedinsoluble remnants are cooled by keeping in a desiccator with a silicagel (25° C.) for 30 minutes. After cooling the insoluble remnants, atotal weight of the dried insoluble remnants of the detergent, the sieveand the collected vessel is measured, and the dissolution ratio (%) ofthe detergent particles is calculated by Equation (1):Dissolution Ratio (%)={1−(T/S)}×100   (1)wherein S is a weight (g) of the detergent particles supplied; and T isa dry weight (g) of insoluble remnants of the detergent particlesremaining on the sieve when an aqueous solution prepared under the abovestirring conditions is filtered with the sieve (drying conditions:maintaining at a temperature of 105° C. for 1 hour, and thereaftermaintaining for 30 minutes in a desiccator (25° C.) containing silicagel).

6. Flowability Properties

The flow time is preferably 10 seconds or shorter, more preferably 8seconds or shorter, still more preferably 7 seconds or shorter. The flowtime refers to a time period required for cascading 100 mL of powderfrom a hopper used in a measurement of bulk density as defined in JIS K3362.

Method for Evaluating Qualities

The methods for determining the qualities of the above-mentioneddetergent particles are described below.

1. Caking Property (Storage Stability)

The caking property evaluated as the sieve permeability is preferably90% or more, more preferably 95% or more. The testing method for cakingproperty is as follows.

An open-top box having dimensions of 10.2 cm in length, 6.2 cm in width,and 4 cm in height is made out of a filter paper (No. 2, manufactured byADVANTEC) by stapling the filter paper at four corners. A total weightof 15 g+250 g of an acrylic resin plate and a lead plate (or an ironplate) are placed on the box charged with a 50 g sample. The box isallowed to stand in a thermostat kept at a temperature of 30° C. and ahumidity of 80%, and the caking state after for 7 days or 1 month isevaluated.

The evaluation is made by calculating the sieve permeability as follows.

(Sieve Permeability)

A sample obtained after the test is gently placed on a sieve (sieveopening: 4760 μm, as defined by JIS Z 8801), and the weight of thepowder passing through the sieve is measured. The permeability based onthe sample obtained after the test is calculated.$\text{Sieve~~Permeability~~(\%)} = {\frac{\begin{matrix}\text{Weight~~(g)~~of~~Powder} \\\text{Passing~~Through~~Sieve}\end{matrix}}{\text{Weight~~(g)~~of~~Whole~~Sample}} \times 100}$

2. Bleed-out Property

As to the bleed-out property of the detergent particles, it ispreferable when the evaluation by the following test methods ispreferably 2 rank or better, more preferably 1 rank. The testing methodfor bleed-out property is as follows: Bleed-out state of a surfactant isvisually examined at bottom (side not contacting with powder) of thevessel made of the filter paper after the caking test. The evaluation ofthe bleed-out property is made based on the area of wetted portionoccupying the bottom in the following 1 to 5 ranks. Incidentally, thestate for each rank is as follows:

-   Rank 1: not wetted;-   Rank 2: about ¼ of the bottom area being wetted;-   Rank 3: about ½ the bottom area being wetted;-   Rank 4: about ¾ of the bottom area being wetted; and-   Rank 5: the entire bottom area being wetted.

3. Particle Size Distribution

As an index of the particle size distribution, the Rosin-Rammler numberis calculated by fitting the 1410 μm-sieve-passed detergent particles,to determine the particle size distribution. The Rosin-Rammler number(n) is calculated using the following equation:log (log (100/R(Dp)))=n log (Dp/De)

-   R (Dp): cumulative ratio [%] of powder having a particle size of Dp    μm or more;-   Dp: particle size [μm];-   De: average particle size [μm]; and-   n: Rosin-Rammler number [−].

The larger the Rosin-Rammler number (n), the sharper the particle sizedistribution. n is preferably 2.0 or more, more preferably 2.5 or more,still more preferably 3.0 or more.

As described above, since the detergent particles of the presentinvention have excellent storage stability and dissolubility and a sharpparticle size distribution, the detergent particles can be suitably usedfor detergent compositions for laundry items.

As described above, the preferred embodiments of the present inventionare as follows:

[1] detergent particles obtained by a process comprising the step ofdry-neutralizing base particles comprising a water-soluble solid alkaliinorganic substance (A) with a liquid acid precursor (B) of a non-soapanionic surfactant, wherein the base particles are obtained by aspray-drying method, and wherein the base particles contain thecomponent (A) in an amount of equal to or greater than 4 times theamount equivalent for neutralizing the component (B) and have an averageparticle size of from 150 to 400 μm;

[2] the detergent particles according to the above [1], furthercomprising a fluidizing aid (C);

[3] the detergent particles according to the above [1] or [2], whereinthe amount of the component (B) is 15 parts by weight or more, based on100 parts by weight of the base particles;

[4] base particles having an average particle size of from 150 to 400μm, comprising 20 to 80% by weight of a water-soluble solid alkaliinorganic substance;

[5] the base particles according to the above [4], further comprising awater-soluble inorganic salt;

[6] the base particles according to the above [4] or [5], furthercomprising a chelating agent;

[7] the base particles according to any one of the above [4] to [6],further comprising a polymer;

[8] the base particles according to any one of the above [4] to [7],further comprising a surfactant;

[9] the base particles according to any one of the above [4] to [8],wherein the particle strength is 100 g/cm² or more;

[10] a process for preparing detergent particles comprising the stepsof:

(a): preparing a slurry comprising a water-soluble solid alkaliinorganic substance (A) in an amount equal to or greater than 4 timesthe amount equivalent for neutralizing a liquid acid precursor (B) of anon-soap anionic surfactant to be added in step (c);

(b): spray-drying the slurry obtained in step (a) to give baseparticles; and

(c): mixing the liquid acid precursor (B) with the base particlesobtained in step (b) and dry-neutralizing the resulting mixture;

[11] the process for preparing detergent particles according to theabove [10], wherein the base particles and the component (B) are mixedwithout applying a cutting power in the step (c);

[12] the process for preparing detergent particles according to theabove [10] or [11], further comprising the step of:

(d): adding a fluidizing aid (C) to the detergent particles obtained instep (c), thereby surface-modifying the detergent particles; and

[13] a detergent composition comprising the detergent particles asdefined in any one of the above [1] to [3].

EXAMPLE 1 Preparation of Base Particles

Base particles were prepared by the following procedures.

The amount 492.3 kg of water was added to a 1 m³-mixing vessel havingagitation impellers. After the water temperature reached 55° C., 128.9kg of sodium tripolyphosphate and 211.3 kg of sodium sulfate weresequentially added thereto. The jacket was set at 45° C. After agitatingthe mixture for 10 minutes, 12.9 kg of a 40% by weight-aqueous sodiumpolyacrylate solution and 154.6 kg of sodium carbonate were addedthereto, and the resulting mixture was then agitated for 60 minutes,with pulverizing under circulation in a line mill, to give a homogeneousslurry. The final temperature of this slurry was 50° C. In addition, thewater content of this slurry was 50% by weight. Incidentally, theaverage particle size of fine particles present in this slurry wasdetermined using an FBRM system. As a result, the average particle sizewas 28 μm.

This slurry was sprayed at a spraying pressure of 35 kg/cm² with apressure spray nozzle arranged near the top of a spray-drying tower. Ahigh-temperature gas fed to the spray-drying tower was supplied at atemperature of 240° C. to the bottom of the tower and exhausted at atemperature of 107° C. from the top of the tower. The composition andthe properties of the resulting base particle are shown in Table 1.Incidentally, the base particle was directly observed with an SEM. As aresult, fine particles were present in the base particle, as shown inFIG. 1.

Preparation of Detergent Particles

The amount 3.0 kg of the base particles obtained by the above-mentionedprocedures were supplied into a Lödige Mixer (manufactured by MatsuzakaGiken Co., Ltd.; capacity: 20 L; equipped with a jacket), and therotation of a main shaft was started at 70 r.p.m., without rotating achopper. Incidentally, hot water at 80° C. was allowed to flow throughthe jacket at 10 L/minute. A mixed solution of 0.75 kg of an acidic formof LAS (liquid acid precursor of an anionic surfactant) and 0.06 kg ofsulfuric acid, which was temperature-controlled to 60° C., was suppliedinto the above mixer in 1 minute, and the components were then mixed andagitated for 4 minutes to carry out a dry-neutralization reaction (theamount of the alkali in the base particles: 7.3 times the amountequivalent for neutralizing the anionic surfactant, 4.8 times the amountequivalent for neutralization by the acid).

Subsequently, 0.51 kg of a zeolite A-type was added thereto, andthereafter a surface modification was carried out with rotating the mainshaft at 150 r.p.m. and the chopper at 3600 r.p.m., to give detergentparticles. The composition, the properties and the quality of theresulting detergent particles are shown in Table 2. Incidentally, thedegree of particle growth of the resulting detergent particles was 1.25.

The resulting detergent particles were particles which had an excellentdissolubility, a sharp particle size distribution and a low cakingproperty.

EXAMPLE 2 Preparation of Base Particles

Base particles were prepared by the following procedures.

The amount 434.5 kg of water was added to a 1 m³-mixing vessel havingagitation impellers. After the water temperature reached 55° C., 178.6kg of sodium sulfate and 127.6 kg of sodium tripolyphosphate weresequentially added thereto. The jacket was set at 45° C. After agitatingthe mixture for 10 minutes, 25.5 kg of a 40% by weight-aqueous sodiumpolyacrylate solution, 153.1 kg of sodium carbonate, 63.8 kg of 40% byweight-No. 2 Sodium Silicate, and 17.0 kg of 30% by weight-LAS-Na wereadded thereto, and the resulting mixture was then agitated for 60minutes, with pulverizing under circulation in a line mill, to give ahomogeneous slurry. The final temperature of this slurry was 52° C. Inaddition, the water content of this slurry was 50% by weight.Incidentally, the average particle size of fine particles present inthis slurry was determined using an FBRM system. As a result, theaverage particle size was 27 μm.

This slurry was sprayed at a spraying pressure of 35 kg/cm² with apressure spray nozzle arranged near the top of a spray-drying tower. Ahigh-temperature gas fed to the spray-drying tower was supplied at atemperature of 242° C. to the bottom of the tower and exhausted at atemperature of 112° C. from the top of the tower. The composition andthe properties of the resulting base particle are shown in Table 1. Thebase particle was directly observed with an SEM, as in Example 1. As aresult, fine particles were present in the base particles.

Preparation of Detergent Particles

Thirty kilograms of the base particles obtained by the above-mentionedprocedures were supplied into a Ribbon Mixer (manufactured by FujiPaudal Co., Ltd.; whole capacity: 90 L; equipped with a jacket), and therotation was initiated at a rotational speed of 67 r.p.m., with a Froudenumber of 0.85. Incidentally, hot water at 80° C. was allowed to flowthrough the jacket at 10 L/minute. The amount 7.5 kg of an acidic formof LAS, which was temperature-controlled to 60° C., was suppliedthereinto in 1 minute, and the components were then mixed and agitatedfor 5 minutes to carry out a dry-neutralization reaction (the amount ofthe alkali in the base particles: 7.3 times the amount equivalent forneutralizing the anionic surfactant).

Subsequently, 2.5 kg of the above mixture and 0.34 kg of a zeoliteA-type were supplied into a Lödige Mixer (manufactured by MatsuzakaGiken Co., Ltd.; capacity: 20 L; equipped with a jacket), and thereaftera surface modification was carried out with rotating the main shaft at150 r.p.m. and the chopper at 3600 r.p.m., to give detergent particles.The composition, the properties and the quality of the resultingdetergent particles are shown in Table 2. Incidentally, the degree ofparticle growth of the resulting detergent particles was 1.08.

The resulting detergent particles were particles which had an excellentdissolubility, a sharp particle size distribution and a low cakingproperty.

EXAMPLE 3 Preparation of Base Particles

Base particles were prepared by the following procedures.

The amount 456.3 kg of water was added to a 1 m³-mixing vessel havingagitation impellers. After the water temperature reached 55° C., 92.9 kgof 40% by weight-No. 2 sodium silicate and 218.4 kg of sodium sulfatewere sequentially added thereto. The jacket was set at 45° C. Afteragitating the mixture for 10 minutes, 46.5 kg of a 40% by weight-aqueoussodium polyacrylate solution and 185.9 kg of sodium carbonate were addedthereto, and the resulting mixture was then agitated for 60 minutes,with pulverizing under circulation in a line mill, to give a homogeneousslurry. The final temperature of this slurry was 45.7° C. In addition,the water content of this slurry was 54% by weight. Incidentally, theaverage particle size of fine particles present in this slurry wasdetermined using an FBRM system. As a result, the average particle sizewas 22 μm.

This slurry was sprayed at a spraying pressure of 35 kg/cm² with apressure spray nozzle arranged near the top of a spray-drying tower. Ahigh-temperature gas fed to the spray-drying tower was supplied at atemperature of 240° C. to the bottom of the tower and exhausted at atemperature of 107° C. from the top of the tower. The composition andthe properties of the resulting base particle are shown in Table 1. Thebase particle was directly observed using an SEM, as in Example 1. As aresult, fine particles were present in the base particles.

Preparation of Detergent Particles

The amount 2.5 kg of the base particles obtained by the above-mentionedprocedures were supplied into a Lödige Mixer (manufactured by MatsuzakaGiken Co., Ltd.; capacity: 20 L; equipped with a jacket), and therotation of a main shaft was started at 70 r.p.m., without rotating achopper. Incidentally, hot water at 80° C. was allowed to flow throughthe jacket at 10 L/minute. The amount 0.78 kg of an acidic form of LAS(liquid acid precursor of an anionic surfactant), which wastemperature-controlled to 60° C., was supplied into the above mixer in 1minute, and the components were then mixed and agitated for 4 minutes tocarry out a dry-neutralization reaction (the amount of the alkali in thebase particles: 7.8 times the amount equivalent for neutralizing theanionic surfactant, 7.8 times the amount equivalent for neutralizationby the acid).

Subsequently, 0.83 kg of a zeolite A-type was added thereto, andthereafter a surface modification was carried out with rotating the mainshaft at 150 r.p.m. and the chopper at 3600 r.p.m., to give detergentparticles. The composition, the properties and the quality of theresulting detergent particles are shown in Table 2. Incidentally, thedegree of particle growth of the resulting detergent particles was 1.38.

The resulting detergent particles were particles which had an excellentdissolubility, a sharp particle size distribution and a low cakingproperty.

EXAMPLE 4 Preparation of Detergent Particles

The amount 2.5 kg of the base particles obtained by the procedures inthe above-mentioned Example 3 were supplied into a Lödige Mixer(manufactured by Matsuzaka Giken Co., Ltd.; capacity: 20 L; equippedwith a jacket), and the rotation of a main shaft was started at 70r.p.m., without rotating a chopper. Incidentally, hot water at 80° C.was allowed to flow through the jacket at 10 L/minute. The amount 0.73kg of an acidic form of LAS (liquid acid precursor of an anionicsurfactant), which was temperature-controlled to 60° C., was suppliedinto the above mixer in 1 minute, and the components were then mixed andagitated for 4 minutes to carry out a dry-neutralization reaction (theamount of the alkali in the base particles: 8.4 times the amountequivalent for neutralizing the anionic surfactant, 8.4 times the amountequivalent for neutralization by the acid).

Subsequently, 1.03 kg of pulverized sodium tripolyphosphate was addedthereto, and thereafter a surface modification was carried out withrotating the main shaft at 150 r.p.m. and the chopper at 3600 r.p.m., togive detergent particles. The composition, the properties and thequality of the resulting detergent particles are shown in Table 2.Incidentally, the degree of particle growth of the resulting detergentparticles was 1.33.

The resulting detergent particles were particles which had an excellentdissolubility, a sharp particle size distribution and a low cakingproperty.

EXAMPLE 5

The amount 2.5 kg of the base particles obtained by the procedures inthe above-mentioned Example 1 were supplied into a Lödige Mixer(manufactured by Matsuzaka Giken Co., Ltd.; capacity: 20 L; equippedwith a jacket), and the rotation of a main shaft was started at 150r.p.m., without rotating a chopper. Incidentally, hot water at 80° C.was allowed to flow through the jacket at 10 L/minute.

The amount 0.23 kg of a nonionic surfactant (EMULGEN 108 KM,manufactured by Kao Corporation), which was temperature-controlled to60° C., was supplied into the above mixer in 1 minute, and thecomponents were mixed and agitated for 1 minute. Next, 0.80 kg of anacidic form of LAS (liquid acid precursor of an anionic surfactant),which was temperature-controlled to 60° C., was supplied into the abovemixer in 2 minutes, and the components were then mixed and agitated for4 minutes to carry out a dry-neutralization reaction (the amount of thealkali in the base particles: 5.7 times the amount equivalent forneutralizing the anionic surfactant, 5.7 times the amount equivalent forneutralization by the acid).

Subsequently, 0.43 kg of a zeolite A-type and 0.30 kg of pulverizedsodium tripolyphosphate were added thereto, and thereafter a surfacemodification was carried out with rotating the main shaft at 200 r.p.m.and the chopper at 2000 r.p.m., to give detergent particles. Thecomposition and the properties of the resulting detergent particles areshown in Table 2.

The resulting detergent particles were particles which had an excellentdissolubility, a sharp particle size distribution and a low cakingproperty.

EXAMPLE 6 Preparation of Detergent Particles

The amount 2.5 kg of the base particles obtained by the procedures inthe above-mentioned Example 1 were supplied into a Lödige Mixer(manufactured by Matsuzaka Giken Co., Ltd.; capacity: 20 L; equippedwith a jacket), and the rotation of a main shaft was started at 150r.p.m., without rotating a chopper. Incidentally, hot water at 80° C.was allowed to flow through the jacket at 10 L/minute.

The amount 0.23 kg of a nonionic surfactant (EMULGEN 108 KM,manufactured by Kao Corporation) and 0.05 kg of water, which weretemperature-controlled to 60° C., were supplied into the above mixer in1 minute, and the components were then mixed and agitated for 1 minute.Next, 0.80 kg of an acidic form of LAS (liquid acid precursor of ananionic surfactant), which was temperature-controlled to 60° C., wassupplied into the above mixer in 2 minutes, and the components were thenmixed and agitated for 4 minutes to carry out a dry-neutralizationreaction (the amount of the alkali in the base particles: 5.7 times theamount equivalent for neutralizing the anionic surfactant, 5.7 times theamount equivalent for neutralization by the acid).

Subsequently, 0.43 kg of a zeolite A-type and 0.25 kg of pulverizedsodium tripolyphosphate were added thereto, and thereafter a surfacemodification was carried out with rotating the main shaft at 200 r.p.m.and the chopper at 2000 r.p.m., to give detergent particles. Thecomposition and the properties of the resulting detergent particles areshown in Table 2.

The resulting detergent particles were particles which had an excellentdissolubility, a sharp particle size distribution and a low cakingproperty. TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Composition ofBase Particles (% by weight) Component (A) Sodium Carbonate 30 30 40 4030 30 Others Sodium Tripolyphosphate 25 25 0 0 25 25 Sodium Sulfate 4135 47 47 41 41 LAS-Na 0 1 0 0 0 0 Sodium Polyacrylate 1 2 4 4 1 1 No. 2Sodium Silicate 0 5 8 8 0 0 Water 3 2 1 1 3 3 Properties of BaseParticles Bulk Density [g/L] 580 381 447 447 580 580 Average ParticleSize [μm] 269 294 231 231 269 269 Particle Strength [g/cm²] 238 150 125125 238 238

TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Composition of DetergentParticles (parts by weight) Base Particles 100 100 100 100 100 100Component (B) Liquid Acid Precursor Acid Form of LAS 25 25 31 29 32 32Others Sulfuric Acid 2 0 0 0 0 0 Nonionic Surfactant 0 0 0 0 9 9 Water 00 0 0 0 2 Component (C) Zeolite A-type 17 17 33 0 17 17 SodiumTripolyphosphate 0 0 0 41 12 10 Production Efficiency Proportion ofParticles Having Size 91 95 95 92 91 93 of 1410 μm or less [% by weight]Properties of Detergent Particles Bulk Density [g/L] 587 446 526 490 680710 Average Particle Size [μm] 336 317 319 306 303 288 60-secondsDissolution Rate [%] 95 96 98 96 94 96 Flowability [s] 6.2 6.4 5.9 6.36.3 6.2 Quality of Detergent Particles Rosin-Rammler Number [—] 3.143.34 2.63 2.76 2.53 2.61 Sieve Permeability [%] 100 100 100 100 100 100(after 7 days) Bleed-out Property [—] 1 1 1 1 1 1

INDUSTRIAL APPLICABILITY

Since the detergent particles of the present invention have excellentstorage stability and dissolubility, and a sharp particle sizedistribution, there is exhibited an effect that detergent compositionswhich are suitably used for laundry detergents can be obtained by usingthe above detergent particles. The detergent particles of the presentinvention are suitable for laundry detergents, dishwashing detergentsand the like.

1. Detergent particles obtained by a process comprising the step ofdry-neutralizing base particles comprising a water-soluble solid alkaliinorganic substance (A) with a liquid acid precursor (B) of a non-soapanionic surfactant, wherein the base particles are obtained by aspray-drying method, and wherein the base particles contain thecomponent (A) in an amount of equal to or greater than 4 times theamount equivalent for neutralizing the component (B) and have an averageparticle size of from 150 to 400 μm.
 2. Base particles having an averageparticle size of from 150 to 400 μm, comprising 20 to 80% by weight of awater-soluble solid alkali inorganic substance.
 3. A process forpreparing detergent particles comprising the steps of: (a): preparing aslurry comprising a water-soluble solid alkali inorganic substance (A)in an amount equal to or greater than 4 times the amount equivalent forneutralizing a liquid acid precursor (B) of a non-soap anionicsurfactant to be added in step (c); (b): spray-drying the slurryobtained in step (a) to give base particles; and (c): mixing the liquidacid precursor (B) with the base particles obtained in step (b) anddry-neutralizing the resulting mixture.
 4. The process for preparingdetergent particles according to claim 3, further comprising the stepof: (d) adding a fluidizing aid (C) to the detergent particles obtainedin step (c), thereby surface-modifying the detergent particles.
 5. Adetergent composition comprising the detergent particles as defined inclaim 1.